How do considerations of gender and reproductive biology figure into intergenerational transfer behavior? Does a parent's support for a child depend upon whether the parent is a father or mother, or whether the child is a son or daughter? Despite recent progress, the majority of studies are gender-blind. The proposed research gives more attention to the distinct constraints and interests of mothers, fathers, sons and daughters that emanate from biological considerations. It focuses on two prominent themes in reproductive biology: The first is paternity uncertainty. How might it affect incentives to provide for children? Might paternity uncertainty generate differences in the transfer behavior between, say, maternal grandmothers (whose biological relationship to grandchildren is always certain) versus paternal ones? The second theme is reproductive and economic prospects of male versus female offspring. A well provisioned son can in principle "go forth and multiply" by having children with several mates. But a daughter can only "go forth and add." Might these considerations spur sex-biased parental investments? Though a biological perspective is novel within economics, the underlying methods are well established. The proposed project will use the Indonesian Family Life Survey (IFLS) and four U.S. household surveys to investigate: (1) How much of the difference in contributions of maternal versus paternal grandparents remains after accounting for variation in observable determinants of intergenerational transfers? (2) How does the unexplained maternal/paternal differential in grandparenting vary with cultural milieu, including practices and traditions that have been implicated in behavior connected with concerns about paternity uncertainty? Each of these data sets contains attributes uniquely pertinent to biological basics addressed in the application.